Nano imprint technique with increased flexibility with respect to alignment and feature shaping

ABSTRACT

By forming metallization structures on the basis of an imprint technique, in which via openings and trenches may be commonly formed, a significant reduction of process complexity may be achieved due to the omission of at least one further alignment process as required in conventional process techniques. Furthermore, the flexibility and efficiency of imprint lithography may be increased by providing appropriately designed imprint molds in order to provide via openings and trenches exhibiting an increased fill capability, thereby also improving the performance of the finally obtained metallization structures with respect to reliability, resistance against electromigration and the like.

This application is a divisional of Ser. No. 11/671,688, filed Feb. 6,2007 now U.S. Pat. No. 7,928,004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to the field of fabrication ofmicrostructures, and, more particularly, to a method for definingmicrostructure features on the basis of nano imprint techniques.

2. Description of the Related Art

Fabrication of microstructures, such as integrated circuits, requirestiny regions of precisely controlled size to be formed in a materiallayer of an appropriate substrate, such as a silicon substrate. Thesetiny regions of precisely controlled size are generated by patterningthe material layer, for instance, by performing photolithography andetch processes. For this purpose, in conventional semiconductortechniques, a mask layer is formed over the material layer underconsideration to first define these tiny regions in the mask layer.Generally, a mask layer may consist of or is formed by means of a layerof photoresist that is patterned by a lithographic process, such as aphotolithography process. During a typical photolithography process, theresist may be spin-coated onto the wafer surface and is then selectivelyexposed to ultraviolet radiation. After developing the photoresist,depending on the type of resist, positive resist or negative resist, theexposed portions or the non-exposed portions are removed to form therequired pattern in the layer of photoresist. Since the dimensions ofthe patterns in sophisticated integrated circuits are steadilydecreasing, the equipment used for patterning device features have tomeet very stringent requirements with regard to resolution and overlayaccuracy of the involved fabrication processes. In this respect,resolution is considered as a measure specifying the consistent abilityto print minimum size images under conditions of predefinedmanufacturing variations. One important factor in improving theresolution is represented by the photolithography process, in whichpatterns contained in a photo mask or reticle are optically transferredto the substrate via an optical imaging system. Therefore, great effortsare made to steadily improve optical properties of the lithographicsystem, such as numerical aperture, depth of focus and wavelength of thelight source used.

The quality of the lithographic imagery is extremely important increating very small feature sizes. Of at least comparable importance,however, is the accuracy with which an image can be positioned on thesurface of the substrate. Many types of microstructures, such asintegrated circuits, are fabricated by sequentially patterning materiallayers, wherein features on successive material layers bear awell-defined spatial relationship to one another. Each pattern formed ina subsequent material layer has to be aligned to a corresponding patternformed in the previously patterned material layer within specifiedregistration tolerances. These registration tolerances are caused by,for example, a variation of a photoresist image on the substrate due tonon-uniformities in such parameters as resist thickness, bakingtemperature, exposure and development. Furthermore, non-uniformities ofthe etching processes can also lead to variations of the etchedfeatures. In addition, there exists an uncertainty in overlaying theimage of the pattern for the current material layer to the etchedpattern of the previously formed material layer whilephotolithographically transferring the image onto the substrate. Severalfactors contribute to the ability of the imagery system to perfectlyoverlay two layers, such as imperfections within a set of masks,temperature differences at the different times of exposure and a limitedregistration capability of the alignment tool. As a result, the dominantcriteria, determining the minimum feature size that may finally beobtained, are the resolution for creating features in individualsubstrate layers and the total overlay error to which the aboveexplained factors, in particular the lithographic process, contribute.

The continuous scaling of microstructures requires a correspondingadaptation of photolithography systems with respect to exposurewavelength, beam optics, alignment means and the like in order toprovide the required resolution, which, however, places a high burden onthe tool manufacturers in view of development efforts, while themanufacturers of microstructures are confronted with increasing toolinvestments and significant cost of ownership. Hence, new techniqueshave been proposed for defining microstructure features in respectivematerial layers, while avoiding or reducing some of the problemsassociated with conventional photolithography techniques. One promisingapproach is the nano imprint technique, which is a method formechanically transferring a pattern defined in a mold or die into anappropriate mask layer, which may then be used for patterning thematerial layer under consideration. For example, during themanufacturing of metallization layers of sophisticated semiconductordevices, requiring metal structures with reduced feature sizes, lowparasitic capacitance and high resistance against electromigration,usually the so-called inlaid or damascene technique is used. In thistechnology for forming wiring layers that provide the complex circuitlayout of integrated circuits, an appropriate dielectric material ispatterned to receive trenches and vias, which are subsequently filledwith a highly conductive material, such as copper, copper alloys, silveror any other suitable metal. Hence, the vias, providing the electricalconnection between metal regions of different stacked metallizationlayers, have to be precisely aligned with respect to the metal regions,such as metal lines, wherein the lateral dimensions of the metal linesand vias, at least in lower-lying metallization layers, are comparableto the minimum critical dimensions, thereby requiring highlysophisticated lithography techniques. In addition, the surfacetopography in higher device layers may have to be thoroughly controlledfor optical patterning techniques, which may require highlysophisticated planarization techniques due to the usage of low-kdielectric materials, which may have a reduced mechanical stabilitycompared to “conventional” dielectric materials, such as silicondioxide, silicon nitride and the like. Thus, by avoiding an opticalpatterning regime, respective trenches or vias may be formed on thebasis of nano imprint techniques, wherein a resist material or any othermask material is contacted by a corresponding die having a relief thatincludes respective lines and spaces for forming trenches, when trenchesfor metal lines are to be formed. In a next process step, the mask layermay be used to transfer the pattern from the mask layer into thematerial layer, such as the dielectric material of the metallizationlayer.

Although many problems associated with photolithography may be avoidedby using the nano imprint technique, the trenches defined by the imprintprocess have to be precisely aligned to previously formed vias, therebyalso imposing very stringent constraints on the imprint processtechnique. In other situations, the nano imprint technique suffers fromreduced flexibility with respect to the shaping of openings whendirectly formed in an interlayer dielectric material, since then theadjustment of exposure and/or etch parameters for obtaining, forinstance, a tapered shape, as is used as an efficient control regime inconventional photolithography techniques, may no longer be available.

The present disclosure is directed to various methods that may solve, orat least reduce, some or all of the aforementioned problems.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an exhaustive overview of the invention. It is notintended to identify key or critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome concepts in a simplified form as a prelude to the more detaileddescription that is discussed later.

Generally, the subject matter disclosed herein is directed to atechnique for forming features of microstructures, such as semiconductordevices, using techniques in which a mechanical interaction is used inorder to form or provide a respective feature, such as a conductiveline, a via and the like, within a specified material layer. For thispurpose, an enhanced degree of flexibility is provided in some aspectsby significantly reducing the number of process steps required forforming, for instance, metallization layers of semiconductor devices inthat via openings and trenches may be defined in a common imprintprocess. In other aspects, the sidewall configuration of trenches, viasand the like may be effectively adjusted on the basis of acorrespondingly designed imprint mold or die in order to obtainnon-perpendicular sidewall portions, as may be advantageous for aplurality of specific device features, such as trenches and openings forfeatures in metallization layers and the like. Consequently, by reducingthe process complexity of imprint techniques and/or by providingenhanced flexibility in shaping respective features, the overallperformance of the respective microstructure device may be enhanced atreduced process complexity, since, for instance, any critical alignmentoperations may be reduced and/or the process performance of certaincircuit features may be enhanced, for instance by obtaining an improvedfill behavior, when metallization structures of sophisticatedsemiconductor devices are considered.

According to one illustrative embodiment disclosed herein, a methodcomprises commonly imprinting a via opening and a trench into a moldablematerial layer that is formed above a substrate, wherein the via openingand the trench correspond to features of a metallization structure of amicrostructure device. Furthermore, the method comprises forming a viaand a conductive line on the basis of the via opening and the trench.

According to another illustrative embodiment disclosed herein, a methodcomprises imprinting an opening into a moldable material layer formedabove a substrate, wherein the opening corresponds to a feature of amicrostructure device and has a sidewall portion of non-perpendicularorientation with respect to a bottom of the opening. Furthermore, themethod comprises forming the feature on the basis of the opening,wherein the feature has a non-perpendicular sidewall portion withrespect to a bottom of the feature.

According to yet another illustrative embodiment disclosed herein, amethod comprises forming a metallization layer for a semiconductordevice and mechanically transferring the metallization layer to asubstrate having formed thereon a plurality of circuit elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numerals identify like elements, and in which:

FIGS. 1 a-1 e schematically illustrate cross-sectional views of amicrostructure during the formation of a via/line metallizationstructure in a common imprint process for directly forming therespective openings in an interlayer dielectric material according toillustrative embodiments disclosed herein;

FIGS. 2 a-2 d schematically illustrate cross-sectional views of amicrostructure device during the manufacturing of a via/linemetallization structure based on a common imprint process with asubsequent etch process according to other illustrative embodiments;

FIGS. 3 a-3 e schematically illustrate cross-sectional views duringvarious manufacturing stages for forming a via/line structure on thebasis of a common imprint process with a subsequent removal ofdielectric material according to further illustrative embodiments;

FIGS. 4 a-4 c schematically illustrate a process flow for forming animprint mold or die, i.e., a negative form of a via/line structureaccording to yet other illustrative embodiments;

FIG. 5 schematically illustrates a mechanical transfer of one or moremetallization structures to a substrate including a plurality of circuitelements in accordance with other illustrative embodiments disclosedherein;

FIGS. 6 a-6 c schematically illustrate cross-sectional views of aplurality of imprint molds or die having a non-perpendicular sidewallconfiguration of respective negative forms of metallization features forsemiconductor devices according to illustrative embodiments disclosedherein;

FIGS. 7 a-7 b schematically illustrate cross-sectional views of asemiconductor device during the formation of isolation trenches on thebasis of tapered imprint die or molds according to yet otherillustrative embodiments; and

FIGS. 8 a-8 d schematically illustrate cross-sectional views of asemiconductor device during various manufacturing stages for forming aconductive line, such as a gate electrode, having a modified sidewallconfiguration obtained by an imprint technique according to otherillustrative embodiments disclosed herein.

While the subject matter disclosed herein is susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and are herein described indetail. It should be understood, however, that the description herein ofspecific embodiments is not intended to limit the invention to theparticular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Various illustrative embodiments of the invention are described below.In the interest of clarity, not all features of an actual implementationare described in this specification. It will of course be appreciatedthat in the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

The present subject matter will now be described with reference to theattached figures. Various structures, systems and devices areschematically depicted in the drawings for purposes of explanation onlyand so as to not obscure the present disclosure with details that arewell known to those skilled in the art. Nevertheless, the attacheddrawings are included to describe and explain illustrative examples ofthe present disclosure. The words and phrases used herein should beunderstood and interpreted to have a meaning consistent with theunderstanding of those words and phrases by those skilled in therelevant art. No special definition of a term or phrase, i.e., adefinition that is different from the ordinary and customary meaning asunderstood by those skilled in the art, is intended to be implied byconsistent usage of the term or phrase herein. To the extent that a termor phrase is intended to have a special meaning, i.e., a meaning otherthan that understood by skilled artisans, such a special definition willbe expressly set forth in the specification in a definitional mannerthat directly and unequivocally provides the special definition for theterm or phrase.

Generally, the subject matter disclosed herein relates to a techniquefor forming features of microstructures, such as semiconductor devicesand the like, in which at least some of the photolithography steps arereplaced by an imprint technique in which a feature, or at least a masklayer for forming a feature, is formed by a direct mechanical contactbetween a moldable material and a corresponding imprint mold or nano dieor stamp, wherein, in some aspects, two different types of features maybe formed in a common imprint process in order to reduce the number ofrequired alignment processes and also reduce the number of individualprocess steps, such as deposition steps, planarization steps and thelike. In another aspect, the shaping of respective features may beaccomplished by appropriately designing respective imprint molds inorder to enhance performance of the respective feature and/or enhancethe performance of the respective patterning process. For example, insome illustrative embodiments, tapered vias or trenches may be formed onthe basis of correspondingly designed imprint die or molds in order tosignificantly enhance the fill behavior of a corresponding depositionprocess for reliably filling in a conductive material, such as metals,metal alloys and the like. Consequently, the overall process efficiencyand thus production costs may be reduced, since, at many manufacturingstages, highly cost extensive and complex photolithography steps may beavoided, or respective photolithography processes may be used forforming appropriate imprint molds, thereby considerably “multiplying”the efficiency of the respective photolithography process, since asingle photolithography process may result in a corresponding imprintmold or die that in turn may be used for processing a plurality ofsubstrates.

FIG. 1 a schematically illustrates a microstructure device 100, which,in some illustrative embodiments, may represent a semiconductor devicethat may receive a metallization structure in order to electricallyconnect respective circuit elements, such as transistors, capacitors,resistors and the like, formed therein. In other cases, themicrostructure device 100 may represent a device having formed thereinopto-electronic components and/or mechanical components and the like.The microstructure device 100 may comprise a substrate 101, which mayrepresent any appropriate substrate, such as a silicon-basedsemiconductor substrate that may include a buried insulating layer (notshown), when a silicon-on-insulator (SOI) architecture is considered, inwhich an appropriate semiconductor layer is formed on a respectiveinsulating layer. In other cases, the substrate 101 may represent anyappropriate carrier material having formed thereon an appropriatematerial layer that allows the manufacturing of respective components,at least some of which may require a corresponding metallizationstructure in order to provide the electrical interconnection between therespective circuit elements. In still other cases, the substrate 101 mayrepresent any appropriate carrier material, above which is to be formeda metallization structure that may be transferred to a respectivesemiconductor device in a later stage, as will be described later on inmore detail. In some illustrative embodiments, the substrate 101 mayhave formed therein a plurality of features including respective contactregions 102, which may be provided in the form of highly conductivesemiconductor regions, metal regions and the like. Moreover, a layer ofmoldable material 103 may be formed above the substrate 101, wherein, inthe embodiment illustrated in FIG. 1 a, the layer 103 may represent anappropriate dielectric material for forming therein features of ametallization structure.

For instance, in some illustrative embodiments, the moldable material ofthe layer 103 may be comprised of a dielectric having a relativepermittivity of 3.0 and significantly less, which are typically referredto as low-k dielectrics or even as ultra low-k dielectrics. It should beappreciated in this context that the term “moldable” refers to materialcharacteristics that allow a mechanical contact with an imprint mold ordie, i.e., a negative form of an opening to be formed in the materiallayer 103, so as to deform the moldable material and subsequently toremove the respective imprint die, wherein then the moldable material103 may substantially maintain the deformed shape after removal of theimprint mold. For example, a wide class of thermal plastic materials areavailable which may be brought into a low viscous state upon applyingheat so that in the low viscous state a respective deformation of thematerial 103 may be accomplished, wherein after cooling down the thermalplastic material, the respective deformed shape may be maintained evenafter removal of the deforming imprint die. In other cases, respectivematerials, such as polymer materials, resist materials and the like, maybe provided in a low viscous state and may, after contact with arespective imprint mold, be hardened, for instance on the basis of UVradiation, heat treatment and the like, so as to maintain the deformedshape.

In the embodiment shown in FIG. 1 a, the microstructure device 100 isshown prior to the contact with a respective imprint mold or die 150which may comprise a substrate 151 made of any appropriate material,such as silicon, silicon dioxide, metals, metal alloys, certain plasticmaterials and the like. Furthermore, the imprint mold 150 may comprise aplurality of negative forms 152 of respective complex openings to beformed in the material layer 103. In the embodiment shown, the negativeforms 152 may comprise a via portion 152A and a trench portion 152B,which may correspond to respective vias and metal lines of ametallization structure to be formed in the dielectric layer 103. Forexample, in sophisticated microstructure devices, such as the device100, respective metal lines or other conductive lines having a width ofapproximately 100 nm to several μm may have to be formed, depending onthe level of the metallization structure under consideration and theminimum critical dimensions for any circuit elements of the device 100.

As previously explained, respective features of metallization structuresare typically formed on the basis of photolithography and correspondingetch processes, wherein highly complex lithography tools includinghighly complex alignment entities are required. During a respectivemanufacturing sequence for forming a via and a metal line connectedthereto, irrespective of the process strategy considered, the trench andthe via have to be aligned to each other, which may finally result in arespective alignment error that has to be taken into consideration bythe respective design rules. By using the imprint mold 150 including therespective negative forms 152A of corresponding via openings and thenegative forms 152B representing respective trenches, the vias and metallines are automatically aligned to each other with high precision,thereby reducing process complexity, increasing device performance andenabling the reduction of process margins that usually have to beprovided to take into consideration a certain degree of misalignmentbetween via openings and trenches.

A typical process flow for forming the microstructure device 100 maycomprise the following processes. After the formation of anymicrostructure features, if provided, such as the conductive regions102, or any other circuit elements on the basis of well-establishedtechniques, which may comprise photolithography processes or otherimprint processes, as will be described later on, implantationprocesses, etch techniques, planarization processes and the like, themoldable material of the layer 103 may be formed on the basis of anyappropriate deposition technique. For instance, the layer 103 may beapplied in a low viscous state by spin-on techniques and may bemaintained in the low viscous state, when it is a curable material suchas a specific polymer material, a moldable resist material and the like.In other illustrative embodiments, the layer 103 may be formed by anyappropriate deposition technique and may be appropriately treated so asto transit into a highly deformable state, for instance by heat treatingthe layer 103, when a thermal plastic material is used. Next, theimprint mold 150 is then positioned and aligned relative to themicrostructure 100 on the basis of well-established alignment tools, forinstance using respective mechanical alignment marks (not shown),optical alignment marks and the like. After appropriately positioningthe imprint mold 150 and the microstructure 100 relative to each other,the imprint mold 150 and/or the microstructure device 100 are movedrelatively to each other as indicated by the arrows 153 whilesubstantially maintaining their lateral position.

FIG. 1 b schematically illustrates the microstructure device 100 when itis in contact with the imprint mold 150, wherein the respective negativeforms 152 have deformed the moldable material layer 103 in order todefine the via opening and a trench therein. Thereafter, the layer 103may be treated, for instance by reducing the temperature thereof,hardening the layer 103 by an appropriate treatment, such as UV (ultraviolet) radiation and the like, in order to bring the material of thelayer 103 into a substantially non-deformable state, that is, in a statein which the material layer 103 may substantially maintain its formafter removal of the imprint mold 150 with a desired high degree offidelity.

FIG. 1 c schematically illustrates the microstructure device 100 whenthe imprint mold 150 is removed, as indicated by the arrows 154, therebyleaving, due to the substantially non-deformable state of the material103, a respective imprinted structure 104 comprising a via opening 104Aand a trench 104B, which substantially corresponds in size and shape tothe respective negative forms 152A, 152B, respectively, of the imprintmold 150. It should be appreciated that the imprint mold 150 may have alow adhesion to the material of the layer 103 in its substantiallynon-deformable state, which may be accomplished on the basis of arespective surface treatment or material composition by usingwell-established techniques for nano imprint processes. Moreover, duringcommonly imprinting the via opening 104A and the trench 104B into thelayer 103, the height level of the material in the layer 103 may changedue to the additional volume of the respective negative forms 152,wherein a respective increase of the height level may locally vary,depending on the pattern density of the respective negative forms 152across the substrate 101. When a fluid communication between respectiveportions of the layer 103 across the substrate 101 may not be provided,for instance due to the pattern configuration of the negative forms152B, substantially suppressing a fluid communication in a final stageof positioning the imprint mold 150 in the material 103, the mold 150may have respective fluid channels (not shown) which may provide anefficient communication between different device portions or which mayallow removal of excess material of the layer 103. Consequently, uponremoving the imprint mold 150 from the layer 103 in its substantiallynon-deformable state, a substantially planar surface configuration maybe obtained wherein, depending on whether excess material of the layer103 has been removed prior to bringing the material of layer 103 in itsnon-deformable state, the thickness of the layer 103 may be differentfrom a thickness of the layer 103 as originally deposited. Furthermore,respective material residues 104C may still be present at a bottom ofthe respective via openings 104A due to minor non-uniformities withrespect to the surface topography of the microstructure 100 and/or ofthe imprint mold 150, thereby resulting in a non-perfect mechanicalcontact with the underlying structure, such as the conductive regions102.

FIG. 1 d schematically illustrates the microstructure device 100 in afurther advanced manufacturing stage, in which the structure 100 issubjected to an etch ambient 105 for removing the material residues104C. During the etch process 105, well-established recipes may be usedin order to efficiently remove the residues 104C, wherein, in someillustrative embodiments, a certain degree of selectivity of the etchchemistry of the process 105 with respect to the material of theconductive regions 102 may be provided. In this way, the process time ofthe etch process 105 may be controlled so as to reliably remove theresidues 104C across the entire substrate 101 substantially withoutcausing undue damage in the underlying regions 102. Moreover, due to theetch process 105, material of the layer 103 may be removed outside ofthe via openings 104A, wherein, however, the respective depths of thetrenches 104B may remain substantially the same due to the concurrentmaterial removal within the trench 104B and the horizontal surfaceportions 103S of the layer 103 while the total thickness of the layer103 may be reduced, depending on the degree of over-etching during theprocess 105. Thereafter, the microstructure device 100 may be preparedfor filling the respective structure 104 by a conductive material, suchas a metal, metal alloys and the like, in order to provide a respectivevia and metal line in order to form a respective metallization structureof the microstructure 100.

FIG. 1 e schematically illustrates the microstructure device 100 in afurther advanced manufacturing stage, wherein respective vias 106A areprovided within the previously formed via openings 104A so as to connectto the underlying conductive regions 102. Furthermore, conductive lines106B are formed within the previously defined trenches 104B.Consequently, the material layer 103 representing any appropriatedielectric material may, in combination with the conductive lines 106Band the vias 106A, define a respective metallization layer 107, whereinthe respective conductive lines 106B provide the inner-level electricalconnection, while the vias 106A provide electrical contact to theconductive regions 102, which may represent contact plugs, contactregions of circuit elements, metal regions of lower-lying metallizationlayers and the like. It should be appreciated that, depending on thetechnology node of the microstructure 100 under consideration, lateraldimensions, i.e., in FIG. 1 e the horizontal extensions of the vias 106Aand the conductive lines 106B, may be 100 nm and even significantly lessfor highly advanced semiconductor devices, wherein the respectivedimensions may depend on the device level and the respective currentdensities occurring during operation of the microstructure device 100.Moreover, it should be appreciated that the specific shape of therespective vias and/or conductive lines 106B may vary in accordance withdesign requirements. For example, the width and/or the depth ofrespective conductive lines 106B may be varied within the same devicelevel, thereby providing a high degree of flexibility in adapting therespective metallization structures with respect to operationalconditions, process conditions of deposition techniques and the like.The same holds true for the vias 106A. Furthermore, the vias 106A andthe conductive lines 106B may be formed on the basis of any appropriateconductive material, wherein, in sophisticated applications, highlyconductive metals, such as copper, copper alloy, silver, silver alloyand the like, may be used in order to provide high performancemetallization structures. Depending on the characteristics of theconductive material to be filled into the respective via openings 104Aand trenches 104B, the conductive material may also comprise aconductive barrier material in order to substantially prevent diffusionof metal into the surrounding dielectric material of the layer 103 andthus finally into sensitive device areas and to also substantiallysuppress an unwanted interaction between dielectric material or reactivecomponents contained therein, such as oxygen, fluorine and the like,with the respective conductive material, such as copper, copper alloysand the like.

The microstructure 100 as shown in FIG. 1 e may be formed on the basisof the following processes. After the etch process 105 (FIG. 1 d), insome illustrative embodiments, a respective conductive barrier material(not shown) may be deposited on the basis of any appropriate depositiontechnique, such as sputter deposition, chemical vapor deposition (CVD),electroless plating, atomic layer deposition (ALD) and the like. Forinstance, an appropriate material, such as tantalum, tantalum nitride,titanium, titanium nitride, tungsten, tungsten nitride and the like, maybe deposited by sputter deposition wherein a preceding sputter etchstep, which may be performed as the etch process 105 or as an additionaletch step, may result in a reliable exposure of the underlyingconductive regions 102. Thereafter, an appropriate seed material, suchas copper and the like, may be deposited, for instance by sputterdeposition, electroless deposition and the like, followed by thedeposition of the bulk metal, such as copper, copper alloy, silver,silver alloy and the like. Next, any excess material, such as barriermaterial, seed material and the actual bulk metal, may be removed on thebasis of any appropriate technique, which may include electrochemicaletching, chemical mechanical polishing (CMP) and the like. In someillustrative embodiments, during the respective removal of excessmaterial, a CMP process may be performed, thereby also planarizing thesurface topography of the microstructure device 100, which may alsoremove any unwanted differences in height level, which may have possiblybeen created during the common imprint process for forming the viaopenings 104A and the trenches 104B (FIG. 1 c).

As a result, the metallization layer 107 including the vias 106A and theconductive lines 106B, which may have any appropriate size and shape,may be readily formed in a highly effective process sequence with areduced degree of process complexity, since the vias 106A and the metallines 106B may be formed on the basis of a common lithography processwithout requiring an individual alignment for each component. Moreover,the specific size and shape of the vias and lines 106A, 106B and inparticular an intermediate portion thereof may be designed in accordancewith device requirements without being restricted by photolithographyand etch techniques, as is the case in many conventional patterningregimes. For instance, sidewalls of the vias 106A and/or of the trenches106B may be readily adapted to process and device requirements, as willbe described later on in more detail, substantially without beingrestricted to specific process parameters in process techniques, such asphotolithography and etch processes. Moreover, in the embodiments shownwith respect to FIGS. 1 a-1 e, the vias 106A and the lines 106B may bedirectly formed in the dielectric material of the metallization layer107, i.e., in the moldable material layer 103, thereby also reducingprocess complexity.

With reference to FIGS. 2 a-2 d, further illustrative embodiments of thesubject matter disclosed herein will now be described in more detail, inwhich a high degree of flexibility is obtained with respect to thedielectric material of a metallization layer so that non-moldablematerials may be effectively used, while vias and trenches may still beformed by a common imprint technique.

FIG. 2 a schematically illustrates a microstructure device 200comprising a substrate 201, which may have formed therein conductiveregions 202 to which an electrical connection is to be provided by oneor more metallization layers to be formed above the substrate 201. Withrespect to the components 201 and 202, the same criteria apply aspreviously explained with reference to the microstructure device 100.Furthermore, in this manufacturing stage, a dielectric layer 207 may beprovided above the substrate 201, wherein the material of the dielectriclayer 207 may be selected with respect to its characteristics as aninterlayer dielectric material for a metallization layer. For example,in sophisticated applications, the dielectric layer 207 may comprise alow-k dielectric material. Moreover, a mask layer 203 may be formedabove the dielectric layer 207, which may be comprised of a moldablematerial, that is, a material that may have a highly deformable statewhen mechanically contacted by an imprint mold 250 and which may bebrought into a highly non-deformable state so as to maintain arespective degree of deformation caused by the contact with the imprintmold 250. For example, the mask layer 203 may comprise a moldable resistmaterial, a thermoplastic material and the like. The imprint mold or die250 may comprise a respective substrate 251 having formed thereonrespective negative forms 252 including a negative form 252A for arespective via opening and a corresponding negative form 252Bcorresponding to a trench. With respect to the imprint mold 250, thesame criteria apply as previously explained with reference to the mold150.

During the manufacturing stage as shown in FIG. 2 a, the imprint mold250 is aligned with respect to the microstructure device 200, similarlyas is also described above with respect to the device 100 and the mold150, and then the mold 250 is brought into contact with the mask layer203, as indicated by the arrows 253, wherein the mask layer 203 is in alow viscous or highly deformable state.

FIG. 2 b schematically illustrates the situation when the imprint mold250 is in contact with the mask layer 203, wherein a respectivetreatment, such as a heat treatment and/or UV radiation, is performed inorder to bring the material of the mask layer 203 in a highlynon-deformable state.

FIG. 2 c schematically illustrates the removal of the imprint mold 250,as indicated by the arrows 254, thereby resulting in respective viaopenings 204A and trenches 204B due to the substantially non-deformablestate of the mask layer 203. With respect to the characteristics of theimprint mold 250 in view of surface adhesion and the like, the samecriteria apply as previously explained with reference to the imprintmold 150. Thus, after removal of the imprint mold 250, the patternedmask layer 203 may then be used as an image or mask during a subsequentanisotropic etch process for transferring the via opening 204A and thetrench 204B into the underlying dielectric layer 207.

FIG. 2 d schematically illustrates the microstructure device 200 duringan anisotropic etch process 205, in which an etch chemistry may be usedthat results in a comparable etch rate for the material of the masklayer 203 and the underlying dielectric material of the layer 207.Consequently, a highly anisotropic etch behavior may be established,since a pronounced etch selectivity between the materials of the layers203 and 207 is not required. Thus, during the etch process 205, materialof the mask layer 203 is increasingly removed along with material ofexposed portions of the dielectric layer 207. In this way, the vias 204Aand trenches 204B of the mask layer 203 are increasingly “pushed” intothe dielectric layer 206 so as to finally obtain respective via openings207A and trenches 207B in the dielectric layer 207, wherein a highdegree of etch fidelity may be accomplished due to the highlyanisotropic behavior of the process 205. Thus, at a final stage of theetch process 205, the dielectric layer 207 may be covered by the residueof the mask layer 203, now indicated as 203R, while the etch process 205may be continued in order to reliably expose the respective conductiveregions 202 at the bottom of the via openings 207A, wherein the residue203R may be consumed by the etch process 205. In some illustrativeembodiments, the residue 203R may remain during the final stage of theetch process 205 and subsequently an additional etch process, forinstance a wet chemical process, or a dry chemical process having a highselectivity between the material of the residue 203R and the dielectriclayer 207, may be performed for removing the residue 203R, therebyproviding enhanced process flexibility, since the initial thickness ofthe mask layer 203 is less critical.

After the removal of the residue 203R by the etch process 205 or by asubsequent additional etch step, the further processing for themicrostructure device 200 may be performed in a similar manner as ispreviously described with respect to FIG. 1 e for the device 100. Thatis, any appropriate process sequence may be performed in order to fillin an appropriate conductive material, such as a barrier material, andhighly conductive metals in order to provide respective vias andconductive lines to define, commonly with the dielectric layer 207, arespective metallization layer. Consequently, the respectivemetallization structure may be formed on the basis of a highly efficientimprint process, wherein respective via openings and trenches may beformed in a common process step while additionally a high degree offlexibility in selecting an appropriate dielectric material for ametallization layer is provided.

With reference to FIGS. 3 a-3 d, further illustrative embodiments willnow be described, in which a metallization structure may be formed onthe basis of an efficient imprint technique, wherein a sacrificial layermay be used for defining respective via openings and trenches and forforming the metallization structure.

FIG. 3 a schematically illustrates a cross-sectional view of amicrostructure device 300 comprising a substrate 301 and a layer ofmoldable material 303 formed thereabove. Moreover, an imprint mold 350including a negative form for via openings 352A and for trenches 352B isshown during the removal from the layer 303, which is in a highlynon-deformable state in order to define respective via openings 304A andtrenches 304B therein. With respect to the characteristics of theimprint mold 350, it is referred to the respective components 150 and250 as previously described. Furthermore, the microstructure 300 mayrepresent a microstructure device as previously described with referenceto the devices 100 and 200 or may represent a base component for formingtherein one or more metallization structures. Thus, the substrate 301may represent any appropriate carrier material for forming thereon themoldable material layer 303 and may, in some illustrative embodiments,have formed therein respective circuit elements and conductive regions(not shown), while, in other embodiments, substantially no otherfunctional components may be provided in the substrate 301. The moldablematerial layer 303 may be provided in the form of any appropriatematerial, the dielectric characteristics of which may not be essential,since the layer 303 may be used as a sacrificial layer that may beremoved after forming therein respective vias and metal lines.

FIG. 3 b schematically illustrates the microstructure device 300 in afurther advanced manufacturing stage. Respective vias 306A andconductive lines 306B are formed within the sacrificial layer 303,wherein any appropriate conductive material may be used for forming thevias 306A and the lines 306B. In one illustrative embodiment, anappropriate highly conductive metal, such as copper, copper alloys,silver, silver alloys and the like, may be filled into the respectivevia openings 304A and trenches 304B (FIG. 3 a), wherein a preceding stepfor forming a respective barrier material may not be necessary since thecorresponding barrier characteristics may be provided in a later stage.In some illustrative embodiments, a surface portion of the substrate 301may comprise any appropriate catalyst material, such as palladium,platinum, copper and the like, which may be exposed during the formationof the via openings 304A and the trenches 304B. Hence, highly efficientelectroless plating techniques may be used, for instance on the basis ofcopper and copper alloys, thereby significantly relaxing any constraintswith respect to the fill behavior as are typically encountered inconventional electroplating regimes for reliably filling high aspectratio openings in a bottom to top fashion. Consequently, in combinationwith a highly efficient definition of the respective via openings 304Aand trenches 304B in a common imprint process, an additional reductionin process complexity and process performance with respect to fillbehavior and barrier deposition may be obtained.

FIG. 3 c schematically illustrates the microstructure device 300 duringa selective isotropic etch process 308 for removing the sacrificiallayer 303 selectively to the metallization structure 306. For thispurpose, highly selective etch recipes may be used, wherein a highdegree of flexibility in the selection of appropriate materials isprovided, since the layer 303 is only provided with respect to thedesired characteristics during the common imprint process while thedielectric characteristics thereof are irrelevant.

FIG. 3 d schematically illustrates the microstructure device 300 in afurther advanced manufacturing stage. Here, the device 300 is subjectedto a treatment 309 for forming a respective barrier layer 310 on exposedsurface portions of the metallization structures 306. As previouslyexplained, for a plurality of highly conductive metals, such as copper,copper alloys and the like, a reliable enclosure of the metal isrequired in order to suppress any interaction with the surroundingdielectric material. Furthermore, due to the moderately high currentdensities that may typically be encountered in highly sophisticatedintegrated circuits, electromigration effects may play a dominant rolewith respect to the overall reliability and thus lifetime of respectivemetallization structures. Since electromigration effects are highlycorrelated with the existence of diffusion paths, any interface regionsmay be especially highly critical with respect to electromigration andhence the overall electromigration behavior may depend significantly onthe quality of the respective interfaces with the barrier material.Consequently, due to the provision of the barrier layer 310 without thepresence of a surrounding dielectric material, highly efficientmanufacturing techniques, such as electroless plating, may be used,thereby providing reliable and uniform enclosure of the metallizationstructures 306 while additionally highly effective barrier materials,such as cobalt/tungsten/boron, cobalt/tungsten/phosphorous and the like,may be formed which are known to exhibit a high resistance againstelectromigration effects in combination with copper material.Consequently, by correspondingly exposing the surface portions of themetallization structure 306, the respective materials may be depositedin a self-aligned manner, thereby forming the barrier layer 310 in ahighly uniform fashion. Consequently, the overall performance of therespective metallization structure 306 may be significantly increasedwhile nevertheless reduced process complexity and increased accuracy maybe achieved due to the common patterning of the respective via openings304A and trenches 304B.

FIG. 3 e schematically illustrates the microstructure device 300 duringa deposition process 311 for forming an appropriate dielectric layer 307in order to define, in combination with the metallization structures306, a respective metallization layer. The deposition process 311 mayrepresent any appropriate deposition technique, such as spin-ontechniques, CVD techniques and the like, in order to reliably enclosethe metallization structures 306 with an appropriate dielectricmaterial, which may have a low relative permittivity as may be requiredfor sophisticated integrated circuits. Depending on the characteristicsof the deposition process 311, any excess material of the dielectriclayer 307 may be removed, for instance by CMP, in order to provide asubstantially planar surface topography, wherein the process may bereliably stopped upon exposing upper portions of the barrier layer 310,while, in other illustrative embodiments, CMP may be combined with aselective etch process, which may also be controlled on the basis of theexposure of the barrier layer 310.

With reference to FIGS. 4 a-4 c, further illustrative embodiments willnow be described, in which an appropriate imprint mold or die may beformed so as to provide a negative form for a via opening in combinationwith a trench.

FIG. 4 a schematically illustrates a cross-sectional view of an imprintmold or die 450 in an advanced manufacturing stage. The die 450 maycomprise any appropriate substrate 451, which may represent anyappropriate carrier material having formed thereon a surface portionthat may enable an appropriate patterning in accordance with respectiveprocess techniques. For example, the substrate 451 may represent asilicon substrate having formed thereon a silicon layer, a silicondioxide layer, or any other appropriate material providing the requiredmechanical stability and respective etch characteristics during thesubsequent processing for forming therein a respective negative image orform of via openings and trenches. Corresponding negative forms oftrenches 452B may be formed in an upper portion of the substrate 451 orany appropriate material layer provided on the substrate 451, whereinthe negative forms 452B may be comprised of any appropriate material,such as silicon dioxide, silicon nitride and the like, which may have ahigh etch selectivity with respect to the surrounding material of thesubstrate 451. Moreover, an etch stop layer 455 may be formed above thesubstrate 451 followed by an additional material layer 456, in which maybe formed respective negative forms of via openings 452A. The negativeforms 452A may be comprised of substantially the same material as thenegative forms 452B or may be comprised of a different material,depending on the process and device requirements. In the illustrativeembodiment shown in FIG. 4 a, the material of the layer 456 and thematerial of the negative forms 452A may exhibit a high degree of etchselectivity with respect to a specified etch recipe. For instance, thelayer 456 may be comprised of polysilicon and the like, while thenegative forms 452A may be comprised of silicon dioxide, silicon nitrideand the like.

A typical process flow for forming the imprint mold 450 as shown in FIG.4 a may comprise the following processes. First, the substrate 451 maybe patterned in order to receive respective trenches, which may beaccomplished on the basis of photolithography and respective etchtechniques in order to provide a respective resist mask and patterningthe substrate 451 on the basis of the resist mask. In other illustrativeembodiments, a respective mask layer including a moldable material maybe patterned on the basis of a respective imprint mold and subsequentlythe resulting patterned mask layer may be used as an etch mask fortransferring the respective trenches into the substrate 451. Forexample, respective etch techniques for silicon or any other appropriatematerial are well-established in the art. Thereafter, trenches formed inthe substrate 451 may be filled by an appropriate material, such assilicon dioxide and the like, on the basis of well-establisheddeposition techniques, such as high density plasma CVD, sub-atmosphericCVD and the like. Thereafter, the surface topography may be planarizedby CMP and the etch stop layer 455, for instance comprised of siliconnitride, may be deposited on the basis of well-established processtechniques. The layer 456 may be deposited, for instance by low pressureCVD when provided in the form of a polysilicon material. Subsequently,the layer 456 may be patterned to receive respective openingscorresponding to the negative forms 452A, which may be accomplished onthe basis of photolithography and anisotropic etch processes or on thebasis of an imprint process technique, in which a corresponding moldablematerial layer may be formed above the layer 456 that may then bepatterned by respective imprint techniques, as is also described above.Thereafter, based on a corresponding resist mask or any other etch mask,the layer 456 may be patterned and the respective openings may berefilled by an appropriate material, such as silicon dioxide and thelike. Consequently, the die 450 as illustrated in FIG. 4 a may be formedon the basis of well-established photolithography techniques or on thebasis of imprint techniques in which the negative forms 452B and 452Aare manufactured in subsequent process steps.

FIG. 4 b schematically illustrates the imprint die 450 in a furtheradvanced manufacturing stage. In one illustrative embodiment, aselective etch process 457 may be performed in order to selectivelyremove the material of the layer 456 while substantially maintaining thematerial of the negative forms 452A. For instance, highly selective wetchemical etch processes are well established in the art for selectivelyremoving polysilicon with respect to silicon dioxide. In otherembodiments, highly selective dry etch processes may be used. In otherillustrative embodiments, the etch process 457 may represent a highlyanisotropic etch process based on an etch mask (not shown) thatsubstantially covers the negative forms 452A, which may be directlyformed from the layer 456. For this purpose, the imprint mold 450 may beformed so as to receive the negative forms 452B in a similar way aspreviously described with reference to FIG. 4 a, and subsequently theetch stop layer 455 and the layer 456 may be deposited as describedabove. Thereafter, a respective etch mask, for instance in the form of aresist mask, formed by photolithography or any other mask, for instanceformed by imprint technique, may be used in order to cover the portions452A, which may then be formed during the etch process 457 from thematerial of the layer 456. Consequently, irrespective of the selectedstrategy, the negative forms 452A may be provided after the completionof the etch process 457.

FIG. 4 c schematically illustrates the imprint die 450 during a furtherselective etch process 458 in order to selectively remove material ofthe substrate 451 with respect to the materials of the negative forms452A, 452B. For instance, highly selective etch recipes for removingsilicon with respect to silicon dioxide are well established in the art.In order to reliably control the etch process 458, a corresponding etchstop layer (not shown), which may be comprised of substantially the samematerial as the negative forms 452A, 452B, may be provided for thispurpose. Consequently, after the completion of the etch process 458, therespective negative forms 452A, 452B are exposed and may substantiallyrepresent corresponding via openings and trenches for a metallizationstructure to be formed in other substrates on the basis of a commonimprint process. It should be appreciated that the die 450 may beprepared in any appropriate manner for subsequent imprint processes by,for instance, surface modification processes in order to appropriatelyreduce the surface roughness or adhesion with respect to any appropriatemoldable material. For instance, respective thin surface films may beformed on the basis of appropriate deposition techniques, such as CVD,ALD and the like. In other illustrative embodiments, respective surfacetreatments, for instance by nitridation and the like, may be performedin order to provide the desired surface characteristics. It should alsobe appreciated that, depending on the process techniques, the specificconfiguration, i.e., size and shape of the respective negative forms,may be adjusted on the basis of the preceding process techniques. Forinstance, if a different height for respective negative forms 452B isrequired, corresponding portions of the die 450 may be covered and acorresponding anisotropic etch process may be performed in order toselectively remove material from non-covered negative forms 452B. Inother cases, when the respective etch masks are defined by imprinttechniques, different sizes and forms of the respective negative forms452A, 452B may be obtained on the basis of the respective imprint molds.Consequently, the die 450 may be efficiently used in the processtechniques as previously described with reference to the microstructuraldevices 100, 200 and 300 and may also be used in combination with otherillustrative embodiments still to be described. In still otherillustrative embodiments, the imprint mold 450 may itself be formed as ametallization structure, which may then be “imprinted” on a respectivemicrostructure device, such as the devices 100, 200 and 300 aspreviously described.

FIG. 5 schematically illustrates a metallization structure 550, which,in some illustrative embodiments, may be considered as an “imprint moldor die” that is to be imprinted, i.e., mechanically connected, to arespective microstructure device 500, which may represent asemiconductor device including a plurality of circuit elements 510connected to a respective number of contact portions 511. Themetallization structure 550 may in turn comprise one or moremetallization layers that may have been formed on the basis of theprocess techniques as previously described with reference to therespective metallization layers 107, 207 and 307 or which may be formedaccording to the process flow as described with reference to the imprintdie 450, wherein the respective negative forms may be formed on thebasis of an appropriate metal material. In one illustrative embodiment,the metallization structure 550 may be formed on the basis of respectiveimprint processes for commonly patterning respective metal lines 552B incombination with respective vias 552A, as is previously described,wherein a plurality of respective process sequences may be repeated inorder to provide a plurality of metallization layers, if desired. Themetallization structure 550 may then be aligned with respect to thedevice 500 on the basis of alignment procedures as previously described.Moreover, in some illustrative embodiments, a “moldable” layer 503 maybe provided, for instance in the form of a thin layer of an appropriateelectrolyte solution from which, upon contact of the metallizationstructure 550 with the layer 503, a selective material deposition may beinitiated in order to provide electrical and mechanical contact with thecontact portions 511. Thereafter, excess material of the layer 503 maybe removed and may be replaced by an appropriate dielectric material,which may be applied in a highly viscous state.

Consequently, the metallization structure 550 may be formed on the basisof highly efficient imprint techniques, as previously described, whereina high degree of decoupling of the process of forming the metallizationstructure of respective semiconductor devices and the manufacturingsequence for forming circuit elements may be achieved. In this way, thetotal manufacturing time for a completed device including themetallization structure 550 and the semiconductor device 500 may besignificantly reduced, while additionally process flexibility and yieldmay improve since any failures in the metallization structure or in thedevice level may not result in a loss of a complete microstructuredevice.

With reference to FIGS. 6 a-6 c, further illustrative embodiments willnow be described, in which appropriately designed imprint molds or dieare provided in order to provide appropriate shapes, especially ofsidewall portions, of respective circuit features.

FIG. 6 a schematically illustrates an imprint mold 650 comprising asubstrate 651 and a plurality of negative forms 652 of respectivecircuit features, which, in one illustrative embodiment, may representnegative forms 652A for via openings and negative forms 652B fortrenches for conductive lines of metallization structures. In otherillustrative embodiments, the respective negative forms 652 mayrepresent other circuit elements, such as isolation trenches, gateelectrodes and the like, as will be described later on in more detail.With respect to the material composition of the substrate 651 and thenegative forms 652, the same criteria apply as previously described withreference to the imprint molds 150, 250, 350, 450. In the embodimentshown, at least upper portions of respective sidewalls 652S of thenegative forms 652A, 652B may comprise a non-perpendicular orientationwith respect to a bottom portion 652D, wherein, in one illustrativeembodiment, the respective sidewall portion 652S may define a taperedshape providing an increased width or diameter at a respective upperportion of via openings and trenches, which may efficiently improve thefill behavior during respective deposition techniques.

FIG. 6 b schematically illustrates the imprint mold 650 having formedthereon the negative forms 652A for respective via openings, which maybe advantageous when a patterning process may be performed separatelyfor via openings and trenches. It should be appreciated that thesidewalls 652S of the negative form 652A may not necessarily have acontinuous tapering along the entire depth but may have differentsidewall angles, depending on the device and process requirements. Forinstance, a significant slope of the sidewall portion 652S may only beprovided at an upper portion thereof, while a lower portion may have asubstantially perpendicular orientation with respect to the bottom 652D.However, any other sidewall configuration may be provided, depending onthe device requirements.

FIG. 6 c schematically illustrates the imprint mold 650 including thenegative form 652B for respective trenches wherein an appropriate size,in the present example, a respective tapering of the sidewall portions652S may be provided in accordance with device requirements.

Consequently, upon using the imprint molds 650 for forming respectiveopenings, the fill behavior in the subsequent deposition of a barriermaterial and/or the bulk material may be significantly enhanced, therebyincreasing the reliability of the respective metallization structures,since, for instance, a more reliable deposition of barrier material maysignificantly contribute to an enhanced resistance againstelectromigration and may also provide improved electrical and mechanicalcharacteristics. For example, the imprint mold 650 as shown in FIG. 6 amay be advantageously used in combination with the process techniquesdescribed above, in which respective via openings and trenches areformed in a common imprint process. On the other hand, the imprint molds650 as shown in FIGS. 6 b and 6 c may be advantageously used inrespective process sequences, in which the respective via openings andtrenches are patterned in separate process steps.

With reference to FIGS. 7 a-7 b and 8 a-8 d, further illustrativeembodiments will now be described in which respective imprint moldshaving non-perpendicular sidewall portions may be used for patterningcircuit elements other than metallization structures for sophisticatedintegrated circuits.

FIG. 7 a schematically illustrates a cross-sectional view of asemiconductor device 700 comprising a substrate 701, which may representany appropriate substrate having formed thereon a material layer forforming therein semiconductor elements, such as transistors, capacitorsand the like. For example, the substrate 701 may represent a carriermaterial having formed thereon a silicon-based semiconductor layer forforming therein respective circuit elements. In this respect, asilicon-based semiconductor layer is to be understood as a substantiallycrystalline semiconductor layer comprising a significant amount ofsilicon, for instance approximately 50 atomic percent silicon or more.Moreover, a mask layer 703 may be formed above the substrate 701 and mayhave formed therein respective openings 704A having sidewalls 704S withat least partially a non-perpendicular orientation with respect to abottom 704D of the openings 704A. In one illustrative embodiment, theopenings 704B may represent trenches used for forming correspondingtrenches in the substrate 701, which may act as isolation trenches forsophisticated semiconductor devices in order to define correspondingactive regions in the substrate 701.

A typical process flow for forming the device 700 as shown in FIG. 7 amay comprise the following processes. After the provision of thesubstrate 701, the layer 703 may be formed by any appropriate depositiontechnique, wherein the material of the layer 703 is a moldable material,that is, the layer 703 may be in a state of low viscosity or may behighly deformable when brought into contact with a corresponding imprintmold (not shown) which may have any appropriate shape, as is forinstance explained with reference to FIG. 6 c. Hence, the respectiveimprint mold having respectively designed sidewall portions may resultin the formation of the corresponding openings 704B having a requirednon-perpendicular shape, for instance a tapered configuration as isshown in FIG. 7 a. Thereafter, the imprint mold may be removed, aspreviously described, while the material of the layer 703 is in a highlynon-deformable state. Thereafter, the device 700 may be subjected to acorresponding etch process 705, during which material of the layer 703and the material of exposed portions of the substrate 701 may beremoved, thereby increasingly transferring the opening 704B into thesubstrate 701.

FIG. 7 b schematically illustrates the semiconductor device 700 afterthe completion of the etch process 705, wherein respective openings 706Bare formed in the substrate 701, wherein a desired tapering, that is, anon-perpendicular configuration of the respective sidewall portion 706S,is obtained on the basis of respectively shaped openings 704B. Hence, byproviding the respective imprint molds with a desired size and shape,the respective configuration of the openings 706B may be designed withhigh flexibility without requiring specifically adapted etch techniquesand the like.

FIG. 8 a schematically illustrates a semiconductor device 800 comprisinga substrate 801 having formed thereon a material layer 807, which may,in one illustrative embodiment, comprise any appropriate material, suchas silicon dioxide and the like, which may be compatible with subsequentprocess steps. Moreover, a mask layer 803 may be formed above the layer807 and may have formed therein a corresponding opening 804B having aspecified shape including a non-perpendicular sidewall portion 804S withrespect to a bottom 804D of the opening 804B. In the embodimentillustrated in FIG. 8 a, the opening 804B may have an increased diameterat an upper portion while exhibiting a substantially constant width at alower portion. For example, the opening 804B may represent a gateelectrode to be formed above the substrate 801.

A typical process flow for forming the semiconductor device 800 as shownin FIG. 8 a may comprise similar processes as described above, wherein,after the formation of any isolation structures, which may be formed onthe basis of isolation trenches as shown in FIGS. 7 a and 7 b, thematerial layer 807 may be formed on the basis of well-establisheddeposition techniques. Thereafter, the layer 803 of moldable materialmay be formed on the basis of appropriate techniques and thereafter theopening 804B may be formed on the basis of an appropriately designedimprint mold to obtain the desired configuration of the shape of theopening 804B. In the present example, a substantially constant lowerportion of the substantially constant width may be provided in order toobtain a well-defined gate length, while the upper portion thereof mayprovide enhanced conductivity of the respective gate electrode. Afterthe formation of the opening 804B by correspondingly hardening the layer803 and removing the respective imprint mold, the device 800 may besubjected to a respective anisotropic etch process 805 to commonlyremove material of the layer 803 and of exposed portions of the layer807, thereby increasingly transferring the opening 804B into the layer807.

FIG. 8 b schematically illustrates the device 800 after the completionof the etch process 805, thereby resulting in a corresponding opening807B.

FIG. 8 c schematically illustrates the device 800 in a further advancedmanufacturing stage. Here, a gate insulation layer 812 is formed at thebottom of the opening 807B, wherein the gate insulation layer 812 mayhave any appropriate configuration with respect to material compositionand thickness as is required by respective transistor elements still tobe formed. Moreover, a layer of gate electrode material 813, forinstance polysilicon and the like, may be formed so as to reliably fillthe opening 807B. For this purpose, appropriate deposition techniques,such as low pressure CVD and the like, may be used. Thereafter, anyexcess material of the layer 813 may be removed by CMP.

FIG. 8 d schematically illustrates the device 800 in a further advancedmanufacturing stage. Here the layer 807 is removed so as to maintain agate electrode 813A having an upper portion with a width 813U and havinga lower portion with a width 813L, thereby providing increasedconductivity of the gate electrode 813A while still maintaining arequired gate length that is substantially defined by the width 813L.The gate electrode 813A may be formed on the basis of a highly selectiveetch process, wherein well-established isotropic etch techniques may beused. For instance, if the gate insulation layer 812 may be comprised ofsilicon nitride, well-established isotropic etch recipes may be used inorder to remove the material of the layer 813 when provided in the formof silicon dioxide, selectively to the gate electrode 813A and the gateinsulation layer 812. In other cases, when the gate insulation layer 812may be formed on the basis of silicon dioxide, an appropriate materialmay be selected for the layer 807, for instance silicon nitride, or anyother appropriate material, such as polymer materials and the like,which may only have the capability of enabling a reliable deposition ofthe gate electrode material 813.

As a result, the subject matter disclosed herein provides an enhancedtechnique for patterning features of microstructures and, in someillustrative embodiments, of metallization structures, such as vias andmetal lines, on the basis of imprint techniques, in which processcomplexity may be significantly reduced by avoiding at least somecomplex alignment procedures by commonly imprinting via openings andtrenches. For this purpose, appropriately configured imprint moldsincluding a via and line structure may be used. In other aspects, theshape, in particular the sidewall configuration of respective circuitfeatures, may be adapted on the basis of respectively designed imprintmolds, thereby providing a high degree of flexibility for the formationof circuit elements, such as vias, metal lines, isolation trenches, gateelectrodes and the like, wherein, in addition to the overall size, thesidewall configuration may be adapted so as to include anon-perpendicular portion for improving the manufacturing process and/orthe final performance of the respective circuit feature. Thus, inaddition to a reduced process complexity, an enhanced device performancemay be achieved since, for instance, with respect to metallizationstructures, an enhanced reliability and performance in view ofelectromigration may be obtained. Moreover, the “mechanical” patterningof at least significant portions of a metallization structure mayprovide increased flexibility of forming the respective structures,wherein, in some illustrative embodiments, the formation ofmetallization structures may be completely decoupled from the formationof circuit elements in the device level, which may significantly reducethe overall manufacturing time and increase production yield.

The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. For example, the process steps set forth above may beperformed in a different order. Furthermore, no limitations are intendedto the details of construction or design herein shown, other than asdescribed in the claims below. It is therefore evident that theparticular embodiments disclosed above may be altered or modified andall such variations are considered within the scope and spirit of theinvention. Accordingly, the protection sought herein is as set forth inthe claims below.

1. A method, comprising: imprinting an opening into a moldable materiallayer formed above a substrate, said opening corresponding to a featureof a microstructure device and having a sidewall portion ofnon-perpendicular orientation with respect to a bottom of said opening;forming said feature on the basis of said opening, said feature having anon-perpendicular sidewall portion with respect to a bottom of saidfeature; substantially removing said moldable material layer to exposesurface portions of said feature; and forming a conductive barrier layeron the exposed surface portions to enclose said feature.
 2. The methodof claim 1, wherein imprinting said opening comprises using an imprintmold representing a negative form, said negative form comprising anon-perpendicular sidewall portion with respect to a bottom of saidnegative form.
 3. The method of claim 1, wherein said opening representsat least one of a via opening and a trench for forming metal-containingregions of a metallization layer of said microstructure device.
 4. Themethod of claim 1, further comprising filling said opening with aconductive material so as to form said feature.
 5. The method of claim1, wherein said feature represents one of an isolation trench and a gateelectrode of a semiconductor device.
 6. The method of claim 1, whereinsaid feature represents at least one of a via opening and a trench for ametallization layer of a semiconductor device.